Circumferential arc segment motor cooling fan

ABSTRACT

A cooling fan according to the present invention includes a housing. A fan assembly includes a plurality of fan blades carrying a rotor ring at the outer circumference of the fan assembly. A plurality of stator elements are supported by the housing to confront the rotor ring around only a portion of the outer circumference of the fan assembly. A motor controller is operatively connected to the stator elements to induce force on the rotor ring to turn the fan assembly.

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of Provisional Application No. 60/226,366 filed Aug. 18, 2000 for “Switched Reluctance Motor (SRM)” by C. Nelson, B. Palmer, N. Mohan and A. Jain.

INCORPORATION BY REFERENCE

[0002] The aforementioned Provisional Application No. 60/226,366 is hereby incorporated by reference in its entirety. U.S. Application No. 09/848,544 filed May 3, 2001 for “Brushless DC Ring Motor Cooling System” by C. Nelson and B. Palmer is also hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to a cooling fan, and more particularly to a cooling fan having a circumferential arc segment motor geometry.

[0004] Diesel power applications such as over-the-road trucks, off-road equipment and agricultural equipment require a cooling system to serve a variety of cooling needs in the equipment. These systems typically contain a number of heat exchangers, a cooling fan, and in some cases a fan drive. In cases where a fan drive is not used, the fan is driven by a belt and continually rotates at a fixed ratio to engine speed. At least three sub-systems are served by the cooling fan, including the engine cooling system, the charge air system and air conditioning system. Other systems such as a transmission cooling system and hydraulic cooling system could also be served by the cooling fan.

[0005] Typical fan drives are implemented as a clutch system of some type, such as an on/off clutch, a viscous clutch, or a hydraulic clutch. However, as noted in U.S. application Ser. No. 09/848,544 which has been incorporated herein by reference, clutch driven cooling systems are not able to efficiently control the power diverted to the fan based on the type of cooling requested. A cooling system employing an electromagnetic fan motor for turning the fan in direct relation to the type of cooling requested provides a greater degree of efficiency.

[0006] Existing electromagnetic fan motor systems, such as might be employed in a 12-volt automobile, are configured with the motor located generally around the central axis of the fan, with fan blades extending outward from a central hub around the motor toward a peripheral fan shroud. While this arrangement is satisfactory for many automotive cooling needs, there are some diesel applications in which it would be beneficial to provide more torque for the amount of power supplied and/or greater flexibility in the design of the fan. These benefits could potentially be achieved with a design that is somewhat similar in size and configuration to the designs used by clutch driven fan systems, which have a simple hub that selectively engages the spinning crankshaft and supports any type of suitable fan design, selected based on the desired cooling performance of the system. A novel electromagnetic cooling system for achieving these benefits is the subject of the present invention.

BRIEF SUMMARY OF THE INVENTION

[0007] The present invention is a circumferential arc segment motor cooling fan that includes a fan assembly having a plurality of fan blades carrying a rotor ring at the outer circumference of the fan assembly. A plurality of stator elements are supported by a housing to confront the rotor ring around only a portion of the outer circumference of the fan assembly. A motor controller is operatively connected to the stator elements to induce force on the rotor ring to turn the fan assembly.

[0008] In some embodiments of the invention, a plurality of housings may be provided to support stator elements confronting the rotor ring around portions of the outer circumference of the fan assembly. For example, configurations including two and four housings may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a front elevational view, with a portion shown in section, of a circumferential arc segment motor cooling fan according to a first embodiment of the present invention.

[0010]FIG. 2 is a side section view taken along the vertical axis of the circumferential arc segment motor cooling fan of FIG. 1.

[0011]FIG. 3 is a section view illustrating the fan assembly of the circumferential arc segment motor cooling fan in greater detail.

[0012]FIG. 4 is a diagram illustrating the stator portion of the circumferential arc segment motor cooling fan in greater detail.

[0013]FIG. 5 is a front elevational view, with a portion shown in section, of a circumferential arc segment motor cooling fan according to a second embodiment of the present invention.

[0014]FIG. 6 is a front elevational view, with a portion shown in section, of a circumferential arc segment motor cooling fan according to a third embodiment of the present invention.

DETAILED DESCRIPTION

[0015]FIG. 1 is a front elevational view with a portion shown in section, and FIG. 2 is a side section view taken along the vertical axis, of circumferential arc segment motor (CASM) cooling fan 10 according to a first embodiment of the present invention. In the embodiment shown in FIGS. 1 and 2, which utilizes a brushless DC (BLDC) ring motor geometry, CASM cooling fan 10 includes fan assembly 12 on bearing assembly 13 a around journal 13 b supported by fan support 14, rotor ring 15 carried on the outer circumference of fan assembly 12, permanent magnets 16 on rotor ring 15, and stator housing 18 supporting stator laminations 20 to confront permanent magnets 16. Windings 21 are wound around stator laminations 20 in a three phase arrangement and connected by wiring to motor controller 22. CASM cooling fan 10 is situated in a radiator housing (not shown) in an exemplary embodiment.

[0016] Fan assembly 12 essentially acts as the rotor of CASM cooling fan 10 by carrying rotor ring 15 around its outer circumference. In an exemplary embodiment, rotor ring 15 is molded as part of the blades of fan assembly 12. Rotor ring 15 is approximately as long as the pitch width of the fan blades, and is blended into the end of each of the fan blades. Rotor ring 15 provides some airflow benefits by reducing the tip losses of fan assembly 12, reducing fan noise, and allowing a shroud to be designed in cooperation with rotor ring 15.

[0017] As explained above, windings 21 are wound around stator laminations 20 and connected in a three phase arrangement in stator housing 18. The amount of torque produced by CASM cooling fan 10 is based on the number of interacting stator laminations 20 and rotor permanent magnets 16 (as well as on the amount of power provided to windings 21 by motor controller 22). Therefore, for a particular spacing of stator laminations 20 and rotor permanent magnets 16, the circumferential extent of stator housing 18 determines the number of stator laminations 20 and therefore the number of interacting stator laminations 20 and rotor permanent magnets 16. The extent of stator housing 18 (and the number of stator laminations 20) can therefore be selected based on the torque required for the particular application of CASM cooling fan 10. In the exemplary embodiment shown in FIGS. 1 and 2, stator housing 18 extends along only the lower portion of the outer circumference of fan assembly 12 and rotor ring 15. This extent of stator housing 18 can provide sufficient torque for many applications because of the relatively large diameter of the active portion of the motor.

[0018]FIG. 3 is a section view illustrating fan assembly 12 of the circumferential arc segment motor cooling fan 10 in greater detail, showing the relationship between the rotor and stator portions of cooling fan 10. Fan assembly 12 carries rotor ring 15 around its outer circumference. Rotor ring 15 carries back-iron 24 and permanent magnets 16 facing outward to confront stator laminations 20 located around the outside of fan assembly 12. Stator housing 18 includes stator laminations 20 and windings 21 wound around stator laminations 20, with potting compound 26 or another suitable material filling the remainder of the cavity in stator housing 18 to secure stator laminations 20 and windings 21. In order to operate the fan, a current is provided through windings 21 by motor controller 22 (FIG. 1). The interaction between the current through windings 21 and the magnetic field between stator laminations 20 and rotor permanent magnets 16 induces a force that causes fan assembly 12 to turn.

[0019]FIG. 4 is a diagram with a portion cut away illustrating stator housing 18 of circumferential arc segment motor cooling fan 10 in greater detail. As explained above, stator housing 18 has a circumferential extent that may be selected according to the torque requirements of the cooling system. Stator housing includes a plurality of stator laminations 20 with windings 21 wrapped around them in a three phase arrangement. The configuration of stator housing 18 to fit in the circle-to-square interface portion of the cooling fan makes efficient use of the space provided, while also yielding excellent torque and overall fan performance.

[0020]FIG. 5 is a front elevational view, with portions shown in section, of circumferential arc segment motor (CASM) cooling fan 30 according to a second embodiment of the present invention. CASM cooling fan 30 is identical to CASM cooling fan 10 (FIGS. 1 and 2) except that stator housing 38 is provided in the upper portion of the assembly in addition to stator housing 18 provided in the lower portion of the assembly. In an exemplary embodiment, stator housings 18 and 38 are arranged symmetrically around rotor ring 15. Stator housing 38 supports stator laminations 40 to confront permanent magnets 16. Windings 41 are wound around stator laminations 40 in a three phase arrangement and connected by wiring to motor controller 22. In an exemplary embodiment, a single motor controller 22 is employed to control the current delivered to windings 21 and 41 in stator housings 18 and 38, respectively.

[0021]FIG. 6 is a front elevational view, with portions shown in section, of circumferential arc segment motor (CASM) cooling fan 50 according to a third embodiment of the present invention. CASM cooling fan 50 is identical to CASM cooling fans 10 (FIGS. 1 and 2) except that stator housings 52, 54, 56 and 58 are provided in the four corner portions of the assembly instead of stator housing 18 shown in FIG. 1. In an exemplary embodiment, stator housings 52, 54, 56 and 58 are arranged symmetrically around rotor ring 15. Stator housings 52,54,56 and 58 are all configured in the same manner, and include stator laminations 60 to confront permanent magnets 16 carried by rotor ring 15. Windings 61 are wound around stator laminations 60 in a three phase arrangement and connected by wiring to motor controller 22. In an exemplary embodiment, a single motor controller 22 is employed to control the current delivered to windings 61 in stator housings 52, 54, 56 and 58.

[0022] It will be understood by those skilled in the art that numerous numbers, positions and extents of stator housings may be provided to achieve a desired amount of torque, up to the point where the stator housing extends completely around the outer circumference of fan assembly 12 and rotor ring 15. Typically, the circumferential extent of the stator is substantially less than 360 degrees, due to the large diameter of rotor ring 15 confronted by the laminations and windings of the stator.

Switched Reluctance Motor (SRM) Embodiment

[0023] In an alternative embodiment of the present invention, described generally with respect to FIGS. 1 and 2, CASM cooling fan 10 may employ a SRM rather than a BLDC motor. The SRM turns fan assembly 12 and rotor ring 15 by providing a magnetic attraction between the electromagnetic teeth of the stator (stator laminations 20) and the steel teeth of the rotor (with the steel teeth replacing permanent magnets 16). If one phase of the motor is energized, the rotor teeth closest to the active stator teeth are magnetically attracted. Just before the rotor teeth are aligned with the active stator teeth, power is directed to the next phase. This active phase in turn attracts its closest rotor teeth and so on. In general, a switched, rotating group of magnetic fields constantly attracts the rotor teeth causing the rotor to rotate continuously.

[0024] Similar to the BLDC motor embodiment, SRM stator laminations 20 are located outside the outer diameter of rotor ring 15. The stator does not form a complete circle around rotor ring 15, but instead spans a particular circumferential arc segment defined by the number of stator laminations 20 and active poles of rotor ring 15. The number of active rotor poles is dictated by the operating specifications, which consist of torque, horsepower, speed, voltage and current. The specified torque typically does not require 360 degrees of active poles due to the large diameter of rotor ring 15. The stator arc can be located at any suitable location around the rotor. The arc segment can also be split into multiple segments located at advantageous locations around the rotor.

[0025] The SRM shares many of the benefits of a BLDC motor, as well as other potential advantages. These advantages include the absence of permanent magnets, reduction in assembly costs, simple salient pole winding, stamped steel laminations for rotor ring 15 and stator laminations 20, and the ability to run in very hot environments due to the absence of permanent magnets.

[0026] The present invention, whether implemented as a BLDC motor, a SRM or an alternative type of motor known in the art, has a circumferential arc segment geometry that enables large amounts of torque to be produced for a given diameter of the cooling fan. This geometry also enables the cooling fan to employ any type of hub supporting any type of suitable fan design selected based on the desired cooling performance of the system, similar to the design of a clutch driven cooling fan, due to the provision of the motor around the outer circumference of the assembly that allows the simple hub to be employed. Because of the relatively large diameter of the confronting rotor ring 15 and stator laminations 20, the stator needs only to extend only partially around the circumference of the fan assembly, rather than completely around the fan circumference. This geometry provides advantages in efficiency and expense in some particular applications of the cooling system.

[0027] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 

1. A cooling fan system comprising: a first housing; a fan assembly having an outer circumference and including a plurality of fan blades and a rotor ring carried at the outer circumference of the fan assembly; a first plurality of stator elements supported by the first housing to confront the rotor ring around only a first portion of the outer circumference of the fan assembly; and a motor controller operatively connected to the first plurality of stator elements to induce force on the rotor ring to turn the fan assembly.
 2. The cooling fan system of claim 1, wherein the rotor ring includes a plurality of permanent magnets and the first plurality of stator elements is configured as a brushless DC (BLDC) motor.
 3. The cooling fan system of claim 1, wherein the rotor ring includes a plurality of metal laminations and the first plurality of stator elements is configured as a switched reluctance motor (SRM).
 4. The cooling fan system of claim 1, further comprising: a second housing; and a second plurality of stator elements supported by the second housing to confront the rotor ring around only a second portion of the outer circumference of the fan assembly, the second plurality of stator elements being operatively connected to the motor controller to induce force on the rotor ring to turn the fan assembly.
 5. The cooling fan system of claim 4, wherein the first and second housings are arranged symmetrically around the rotor ring.
 6. The cooling fan system of claim 4, further comprising: a third housing; a fourth housing; a third plurality of stator elements supported by the third housing to confront the rotor ring around only a third portion of the outer circumference of the fan assembly, the third plurality of stator elements being operatively connected to the motor controller to induce force on the rotor ring to turn the fan assembly; and a fourth plurality of stator elements supported by the fourth housing to confront the rotor ring around only a fourth portion of the outer circumference of the fan assembly, the fourth plurality of stator elements being operatively connected to the motor controller to induce force on the rotor ring to turn the fan assembly.
 7. The cooling fan system of claim 6, wherein the first, second, third and fourth housings are arranged symmetrically around the rotor ring.
 8. A cooling fan system comprising: a first housing located in an outer perimeter portion of the fan area; a fan assembly having an outer circumference and comprising: a hub mounted on a journal; and a plurality of fan blades supported by the hub, the fan blades having a configuration selected based on a desired cooling performance of the cooling fan system; a first plurality of stator elements supported by the first housing around a first portion of the outer circumference of the fan assembly; and a motor controller operatively connected to the first plurality of stator elements to induce force on the fan assembly to turn the fan assembly.
 9. The cooling fan system of claim 8, wherein the fan assembly includes a rotor ring carried by the fan blades at the outer circumference of the fan assembly.
 10. The cooling fan system of claim 9, wherein the rotor ring includes a plurality of permanent magnets and the first plurality of stator elements is configured as a brushless DC (BLDC) motor.
 11. The cooling fan system of claim 9, wherein the rotor ring includes a plurality of metal laminations and the first plurality of stator elements is configured as a switched reluctance motor (SRM).
 12. The cooling fan system of claim 8, further comprising: a second housing located in the outer perimeter portion of the fan area; and a second plurality of stator elements supported by the second housing around a second portion of the outer circumference of the fan assembly, the second plurality of stator elements being operatively connected to the motor controller to induce force on the fan assembly to turn the fan assembly.
 13. The cooling fan system of claim 12, wherein the first and second housings are arranged symmetrically around the fan assembly.
 14. The cooling fan system of claim 12, further comprising: a third housing located in the outer perimeter portion of the fan area; a fourth housing located in the outer perimeter portion of the fan area; a third plurality of stator elements supported by the third housing around a third portion of the outer circumference of the fan assembly, the third plurality of stator elements being operatively connected to the motor controller to induce force on the fan assembly to turn the fan assembly; and a fourth plurality of stator elements supported by the fourth housing around a fourth portion of the outer circumference of the fan assembly, the fourth plurality of stator elements being operatively connected to the motor controller to induce force on the fan assembly to turn the fan assembly.
 15. The cooling fan system of claim 14, wherein the first, second, third and fourth housings are arranged symmetrically around the fan assembly. 